The prior art prostheses for the amputee of a hand or forearm are characteristically heavy cumbersome devices that are a poor substitute for a natural hand and forearm, both physically and cosmetically. lt is the prehensile grip and natural appearance that has been lacking in the prior art, and though mechanical arms and hands have been devised, they have been overly engineered, complex and excessive in weight so as to be unnatural in function and in appearance. Accordingly, it is a general object of this invention to provide a prosthesis which involves the hand and forearm and provides a light weight prosthesis having a natural prehensilefunction and a natural cosmetic value as well.
The human body involves a skeletal frame that supports the flesh, the composite of which involves bone, muscle, fat, and a covering of skin, and the total of which has a certain mass and firmness associated with rigidity. In other words, the parts and limbs of the human body have certain expected physical qualities as well as mechanical functions which enable man to perform. In this case under consideration it is dexterity which is to be reastablished with the amputee, enabling him to perform substantially as before, it being an object herein to provide a "biased to grip" prosthesis that operates by forcible entry of an object therein or by deliberate mechanical release of the prehensile mode; to grip and release objects the same as a natural hand. With the present invention, there is a fixed thumb and at least one finger that moves in opposition thereto, preferably the index and/or middle finger, to establish a prehensile grip with an object therebetween. Note that there are two or three gripping members and least one of which is articulated. It is also an object of this invention to provide such a prosthesis wherein the mass is reduced, and a prosthesis wherein natural firmness is obtained, from the standpoints of comfort and appearance.
The anatomy and movement of body members involves motor means and coupling means to the simulated body members to be operated. It is the hand and its moveable index and middle fingers with which this invention is primarily concerned, it being an object herein to simulate the muscles and tendons that formerly motivated said fingers of the amputee. Accordingly, the hand is replaced mechanically as well as cosmetically, and the muscle and tendon complex is replaced by a biased grip and motor means operating the mechanical hand in a natural way. In practice, the prehensile grip is established by spring means and it is the remaining body motions and functions that are employed as the motivating power to release said grip, under mental control to be governed by the amputee. As will be decribed, It is assumed that the upper arm and a portion of the lower arm remain intact, in which case it is the relative angular displacement between the humerus and what remains of the radius and ulna that is employed to operate the prehensile movement of the at least one or more aforementioned mechanical fingers; the thumb being fixed as it is opposed to the moveable index and/or middle finger.
The prosthesis as it is disclosed herein resembles a forearm and natural hand in every respect, having an extension of the radius and ulna, having carpal and metacarpal sections, and having each of the proximal, middle and terminal phlanges of the fingers. It is an object of this invention to articulate each moveable finger (index or middle finger) as a unitary member, so that they are free to move separately and/or together in opposition to the fixed thumb. It is the proximal phalanges or long bone of each finger that is operable as a lever, and with the middle and terminal phalanges adjustably carried thereby and moved therewith. However, a natural feature of this invention is the floating articulation of a pair of fingers (index and middle finger), as may be desired; in each case the phlanges having inward and retractive movement with respect to the metacarpal section carrying the same. In practice, and as shown herein, the index and middle fingers are spring biased to close, whereby the proximal middle and terminal sections oppose an object or the thumb. It is to be understood that any one and/or all of the finger joints can be simulated as described herein.
The motor means and coupling means to the mechanical fingers provided as hereinabove referred to, simulates the tendon system of the natural arm and hand. However, the motor and coupling system herein disclosed is simplified and practical, as it employs flexible members anchored to the amputee's upper arm above the capitulum of the humerous and extended to the proximal phalanges to be moved. A feature is the coordinated movement of both the index and middle finger by yoke means, whereby the biased grip of the prothesis can be released from an object in a natural manner. Another feature is the positive action of a pull cord system, whereby the amputee can intelligently apply decreased grasping pressures as circumstances require.
It is to be understood that the anatomy to be replaced varies widely according to deformation and injury to a person's body, so that it may be any one or more of the fingers that must be replaced, it being an object herein to replace any one of the fingers as herein disclosed. Fundamentally, it is the skeletal frame, flesh and skin that is reestablished and all of which is primarly of plastic material having body thickness, softness and suppleness so as to simulate the skin and finger pads, the fingers and the palm of a real hand. Color, surface texture and imperfections (wrinkles etc.) are included along with filngernails manicured to match the person's other real hand. Accordingly. realism is achieved with the present invention, for practical as well as for psychological purposes.
An object of this invention is to provide an articulation mechanism of unit form that is adapted to occupy the interior of a hand prosthesis of natural form. That is, enlargement of the prosthesis hand is unecessary, as the articulation unit fits well within the natural hand contours; it being understood that several sizes of articulation units are to be provided, for small to large sized hands. It is also an object of this invention to provide proximal and terminal phalanges of the fixed thumb that are adjustable, and wherein each articulated finger has middle and terminal phalanges that are adjustable with respect to the proximal phalanges. It is also an object of this invention to provide for adjustment of the fourth and fifth fingers whereby each phalange thereof can be adjustably positioned for natural opposition to the usual object of be grasped. In practice, a heavy gage maleable wire or rod is used to extend from the metacarpal so as to establish the aforesaid phlanges, to be adjusted as circumstances require.